Final answer:
The dominant theory among scientists and historians is that the Americas were populated by peoples who crossed the Bering Land Bridge from present-day Russia to Alaska during the Ice Age, approximately 15,000 to 30,000 years ago.
Step-by-step explanation:
Most scientists, archaeologists, and historians believe that the Americas were first populated by peoples who crossed the land bridge between present-day Russia and Alaska, known as Beringia. This theory is called the Bering Land Bridge Theory. It suggests that during the Ice Age, sea levels dropped, exposing a vast stretch of land connecting Asia and North America. It's believed that people in search of food crossed this land bridge around 15,000 to 30,000 years ago, gradually populating the Americas. Therefore the corect option is A.
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